The present invention relates to a control apparatus for controlling automated machinery in real time, and particularly to a control apparatus of high performance adapted to provide complex control, such as controlling a robot arm.
The prior apparatus for controlling automated machinery can be represented by a robot controller as disclosed, for example, in "Development of New Type Robot Control Console (Model 4)" by K. Aizawa et al., TOKIKO REVIEW, Vol. 28, No. 1, 1984, p.p. 20-26. As shown in FIG. 3 thereof, the control console fundamentally consists of a main CPU that works as a master processor, peripheral units thereof, and a servo unit. The peripheral units include a variety of types of I/O units, and are connected to a local bus in the main CPU via interface circuits, the local bus being connected to a microprocessor. The servo unit is connected to an externally extended bus that is connected to the local bus via a bus buffer. As optional units, a high-speed arithmetic unit and a hard disc control unit may be additionally connected to the externally extended bus.
The above-mentioned conventional control apparatus lacks extensibility in the processing ability of the main CPU. To supplement the functions, an intelligent subsystem having a CPU may be connected as an I/O unit to the local bus. However, the intelligent subsystem thus connected can do nothing but to passively work as an I/O unit for the main CPU. There are provided no facilities for voluntary communications from the intelligent subsystem to the main CPU. Therefore, the main CPU must control the intelligent subsystem in a top-down manner. Accordingly, the software overhead for controlling the system tends to increase despite a high ability of autonomous operation inherent in the intelligent subsystem.
Moreover, a configuration which is provided with only a single externally extended bus imposes considerable limitations on increasing the hardware amount. The number of elements successfully connectable to a bus is limited for electrical reasons. With reference to communication means between the processor in the main CPU and various units, furthermore, both the hardware architecture and the usage thereof in software lack uniformity. These circumstances also make it difficult to add functions and make it cumbersome to maintain the system.
These disadvantages are detrimental to the realization of many features required for a high-performance control apparatus, such as the extensibility in processing ability and function, the function distribution and modularization that are helpful to inproving the maintainability of hardware, and the easiness in preparing and maintaining software which implements the individual functions.